The impact of vehicle exhaust (especially diesel) on respiratory health is a major concern of community residents of Northern Manhattan and the South Bronx, New York City. While the existence of adverse impacts appears obvious both to residents and health scientists, surprisingly little data are available to firmly establish this linkage. A principal scientific barrier to further insights is the uncertainty surrounding human exposure to diesel and other vehicle exhaust at the community and individual levels. The proposed study will address these uncertainties by 1) measuring ambient concentrations of black carbon (BC), PM2.5, and trace elements at four high schools in the NYC metropolitan area, three of which represent a range of diesel impacts in Harlem and the South Bronx, and one of which is located in an upwind, suburban community, testing the hypothesis that BC concentrations will show a gradient across schools as a function of local diesel traffic density; 2) assess baseline respiratory health status among 300 students at each school, and follow a subset of 40 students for daily symptoms, testing the hypothesis that daily symptoms are associated with daily BC concentrations; 3) in a subset of 20 students at each school, characterize personal exposures to BC, PM2.5, and traffic-related metals, and determine the relative importance of exposures occurring at home, at school, and while commuting in total personal BC exposures; 4) assist participating schools to implement a community air pollution measurement curriculum using materials currently being developed and tested jointly by West Harlem Environmental Action and NIEHS; 5) working with community interns, carry out special studies to collect traffic counts and airborne particle samples associated with high-volume roadways, bus depots, and alternative commuting patterns. This community-driven study should expand our understanding of the relationships between urban traffic sources and personal exposures to vehicle-related particles among young people living and going to school in urban core neighborhoods of Northern Manhattan and the South Bronx.